Order Pairs of Relation R on S: Multiply for Even Result

[sMilips]

Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*b is

Q: Let S = {1,2,5,6 }
Define a relation R on S of at least four order pairs, as (a,b)  R iff a*b is even (i.e. a multiply by b is even)

 

[Olinguito]

Re: Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*

Hi sMilips.

You want $(a,b)$ such that $ab$ is even. So $(2,1)$ is possible since $2\cdot1=2$ is even. But you don’t want $(1,5)$ because $1\cdot5=5$ is odd. Thus $(1,5)\notin R$ but $(2,1)$ can be in $R$ (it doesn’t have to but you can include it if you want). In general, if $ab$ is even, what can you say about one (possibly both) of $a$ and $b$?

 

[sMilips]

Re: Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*

Plz type clear. Did not understand your answer.

 

[Evgeny.Makarov]

Re: Q: Let S = {1,2,5,6 } Define a relation R on S of at least four order pairs, as (a,b)  R iff a*

Plz type clear. Did not understand your answer.

Please write the exact part in Olinguito's answer that you did not understand and why. Also, the answer in post 2 uses so-called LaTeX to show mathematical formulas. If they look garbled somehow on your device but the rest of the text looks OK, please say so. If there are other problems with displaying the thread, please describe it.